A right-handed pitcher snaps his wrists in clockwise rotation when delivering a curveball (he grips the ball with his middle finger near the top of the ball and his thumb on the bottom---but releases the pitch with his thumb near the top). A pitcher throws a slider with smaller wrist-break. He imparts spin by gripping the ball "off-center" (that is, he grips the ball with his middle finger at "2 o'clock"-- instead of 12 o'clock)

Jeff Gordon has been reporting and writing since 1977. His most recent work has appeared on websites such as eHow, GolfLink, Ask Men, Open Sports, Fox Sports and MSN. He has previously written for publications such as "The Sporting News" and "The Hockey News." He graduated from the University of Missouri-Columbia School of Journalism in 1979 with a bachelor's degree.
Baseball players place a tremendous amount of stress on their arms and the ligaments which control how the arms and shoulders move. By practicing pitching drills which focus on developing and loosening these muscles athletes will be taking a step to avoid costly injuries. By adding core work into the pitching drill athletes will further protect their bodies by building a strong base at the center of their body.
Another more advanced variation of the curveball is the knuckle curveball (sometimes called a spike curve). This is the curveball grip that I used. Thrown the same way as my beginners curveball only you'll tuck your finger back into the seam of the ball. Your knuckle will now point to your target instead of your index finger (in the beginners curve).
In order to master the curveball, you must start by gripping the ball with your middle and index fingers together, with the fingers across the seams of the ball at the widest part (the widest distance between the seams). Keeping a tight grip on the ball, especially with the middle finger, don’t let the ball touch the palm of your hand, or you won’t generate enough topspin, which is what allows the ball to drop when it gets close to home plate.
I learned this pitching drill from Coach Scott Birchler who was a high school coach at our rival high school but as I got older and made the transition from player to coach, he helped me a lot. This pitching drill that he taught me is great for any pitcher who wants to be more consistent with their curveball or slider and fixes two of the biggest problems in guys who throw these pitches, dropping that elbow and not finishing the pitch.